Meeting the demand for a display apparatus that can display images represented by an image signal involves developing high contrast and low power consumption configurations and the like. To meet these demands, a local dimming technique is used.
Local dimming is a technique in which the image represented by the image signal is divided into a plurality of divided images and the brightness of each divided image is adjusted in accordance with the brightness level such as the luminance value or the like of each divided image so as to make a dark divided image appear darker and a bright divided image appear brighter.
For example, in the liquid crystal display using LED (Light Emitting Diode) as its backlight, local dimming can be implemented by lowering the output of backlight in the area where the dark divided image is displayed. Since lowering the output of backlight in the area where a dark divided image is displayed makes the dark divided image appear darker, the dynamic range of the displayed image can be widened, hence high-contrast display can be achieved. Further, lowering the output of backlight can also achieve low power consumption.
As the division number of the image is increased in local dimming, the brightness of each of the pixels that form the image will be adjusted last.
An organic EL (Electro Luminescence) display can be regarded as a display in which the brightness of each of the pixels can be adjusted. However, organic EL displays suffer from the problem in which the lifetime of the light source is not sufficiently long.
An image projection apparatus that projects the image by scanning the laser beam output from a light source by use of a MEMS (Micro Electro Mechanical Systems) mirror, can be regarded as another kind of display in which the brightness of each of the pixels can be adjusted.
There are image projection apparatuses other than the image projection apparatus that use the aforementioned MEMS mirror, such as ones that project the image by performing amplitude modulation on the light output from a lamp, LED, laser light source or the like by means of a display device such as a liquid crystal panel, DMD (Digital Micro mirror Device), in accordance with the image signal. These image projection apparatuses can project the image with a simpler configuration compared to the image projection apparatus using a MEMS mirror.
Patent Document 1 (JP2008-544307A) discloses an image projection apparatus which projects the image by performing phase modulation on the laser beam output from the light source in accordance with the image signal. According to the image projection apparatus disclosed in Patent Document 1, it is possible to promote low power consumption because phase modulation on the light output from the light source will not cause any optical loss, unlike in the case of amplitude modulation.